A restricted blood supply to the heart muscle is a condition termed myocardial ischemia which is evidenced by abnormal heart muscle electrical activity. Untreated, myocardial ischemia can ultimately result in heart failure. As a result, monitoring of the electrical signals which stimulate the heart muscle is an invaluable diagnostic tool for determining the health of the heart and identifying abnormalities thereof.
When the electrical signal of a heart muscle is plotted over time, it defines a characteristic curve having a waveform which extends periodically above and below a horizontal reference axis conventionally termed the isoelectric line. Each elevation or depression of the signal curve above or below the reference axis respectively is termed a wave and is identified by a letter. There are a total of six waves in each period of the signal which are identified by the letters, P, Q, R, S, T, and U. A straight line connecting two waves of the signal curve is further identified as a segment, while a wave and connecting straight line is termed an interval. Segments and intervals are identified by various combinations of the above-listed letters.
A normal electrical signal of a healthy heart muscle is generally reflected in a regular curve having predictable PR and ST segments and PR, QRS, and QT intervals. Anomalous electrical signals of a heart muscle are reflected by deviations in specific portions of the curve from the predicted norm. Such deviations, and specifically deviations of the ST segment, may be symptomatic of myocardial ischemia.
Conventional electrical monitoring devices of the heart muscle are usually relatively immobile and complex to operate which requires them to be maintained in a central medical facility for operation by skilled personnel. As a result, outpatients at such facilities only receive monitoring periodically and for a short duration. However, diagnosis of myocardial ischemia generally requires the compilation of signal histories for an extended period of time which periodic monitoring does not provide.
Portable monitors for heart muscle electrical activity represent a potential solution to this problem. Unfortunately, satisfactory portable monitors have not been developed which are sufficiently small to enable full mobility of the patient, yet which are sufficiently sophisticated to enable continuous and reliable electrical monitoring of the patient in remote environments. As such, an electrical monitor is needed which specifically monitors electrical signals of the heart muscle and detects abnormal activity thereof. A monitor is needed which enables recording and displaying of relevant diagnostic data relating to anomalous heart muscle electrical signals. Further, such a monitor is needed which is portable, thereby enabling full mobility of the patient while providing continuous effective operation in remote environments.